Japan has pledged $15.5 million to help countries in the Middle East and Africa that are battling militants from the Islamic State group.

Tokyo's Foreign Minister Fumio Kishida said Tuesday the aid would support counter-terrorism efforts, including increased border control and investigation capabilities.

More details of the aid will be unveiled by Vice Foreign Minister Yasuhide at an international anti-terror conference Thursday in Washington, a foreign ministry statement said.

The counter-terrorism package is twice the amount previously pledged by Kishida during a visit to Brussels last month. Separately, Tokyo has also pledged $200 million to help refugees fleeing Islamic State-controlled areas.

Prime Minister Shinzo Abe has vowed a tough response to the Islamic State militants, who in January beheaded two Japanese hostages - a journalist and his companion.